1. Field
The invention is in the field of tools for use in adjusting and replacing the adjusting pad on the tappets or valve lifters in internal combustion engines, such as the four cycle, dual overhead cam engines generally used in motorcycles and some types of automobiles.
2. State of the Art
In performing a proper tune-up of a motorcycle or similar type engine, it is necessary to determine whether the ajdusting pads in the valve lifters are of correct thickness so as to give proper valve clearance. If not, these adjusting pads must be replaced. With most current tools available, the cam shaft in the engine has to be rotated to the position where the valve is extended or opened to its maximum position, i.e. the cam lobe is in contact with the adjusting pad. A holding tool is then inserted, which is generally secured to the cylinder head using a cylinder head cover bolt hole. The cam then has to be rotated in the opposite direction so that the heel of the cam is toward the adjusting pad, thus giving clearance between the cam and the pad. The tool holds the valve lifter in its extended position while the cam is rotated to provide the clearance. Such tools have to be carefully positioned so that they catch only the bucket of the tappet and not the adjusting pad, and care has to be taken to carefully rotate the cam in only one direction after installation of the tool; otherwise, the cam may be ruined.
Another tool currently available, while not requiring rotation of the cam, is in two pieces, one of which is used to move the valve lifter against its spring tension while the other is placed to hold the valve after being so moved, these two tools require both hands to manipulate which causes problems in the small space available. Also, because one is actively working against the valve spring tension, the tools can easily slip, thereby causing injury to the worker.
In addition to the possible damage to the cam and injury to the worker that can occur using currently available tools, such tools are difficult to use and much time is expended in positioning them and rotating the cams to proper position. Using the current tools, it usually takes about half an hour or more to properly check the adjusting pads. Because of the time and difficulty involved, many times when such adjustments should be checked the mechanics do not do so.